We have with a friend a project of FPV drone. We used a max7456 as an OSD chip, and developed an Arduino library that fitted our needs (Some exist, but most of them are in NTSC mode, and even if the convertion is not hard to make, we made a new one mostly for the "beauty of it" ) . Feel free to make any comment (and of course to navigate over our new website ) http://theboredengineers.com/2012/12/a-max7456-library-for-arduino/